COUPLING FRACTIONING AND HYDROLYSIS REACTORS TO OBTAIN SUGARS FROM BIOMASS

C. M. PIQUERAS; J. GARCÍA-SERNA; FLORENCIA M. YEDRO; DANILO A. CANTERO; M. J. COCERO

York

Conferencia; 11th International Conference on Renewable Resources and Biorefineries; 2015

University of York

One of the main challenges of biomass usage is the efficient depolymerization of cellulose and hemicellulose into its composing monomers or into components of added value. The use of pressurized fluids has been proposed as an environmentally compatible process to integrate the polymerization-reaction-separation processes. Particularly, high-temperature pressurized water has proved to be a good solvent for clean, safe and environmentally benign organic reactions. Great advantages of this medium are been found for biomass processing (e.g. energy saving in the raw material drying, time reduction due to faster reaction rates). For woody biomass (in this case Holm oak), the major disadvantage of the process is the pretreatment, involving the step in the grinding needed to reach particles sizes able to be fluidized (e.g. < 200 micrometers). In order to solve this issue, we have designed a process coupling a subcritical fractionation and a supercritical hydrolysis reactor. In this sense, we can split the major components of biomass, hydrolyze each stream, and obtain the products of the sugars of major composition. The yield of total sugars obtained of the fractionation stage was 65 w/w %, being 20 w/w % xylose as main component of hemicellulose sugars and 45 w/w% of glucose present in the cellulose of the of the raw matter. The product of the sugars decomposition (aldehydes and acids) was below of 15 w/w % being the major components: glycolaldehyde and acetic acid. The control of products derived from the sugars degradation was performed by tuning the temperature and pressure of the hydrolysis stage. For instance below of the water critical point, 300ºC and 25 MPa the reaction medium is highly ionic, favouring the dehydration and autohydrolysis reactions. However, above water critical point at 400ºC and 25 MPa the medium is highly non-ionic, favouring radical reactions. We worked at 385 °C and 25 MPa and residence times in the range of 0,6 an 5,9 s of the hydrolysis stage. The composition of the product stream could be directed from 40% up to 60 w/w % of aldehydes (Glycolaldehyde as the main component) by the route of retro-aldol condensation. These results are promising, taking into account that we are processing natural biomass with a very simple pretreatment.